Process for improving carbon conversion efficiency

ABSTRACT

The invention provides for the integration of a CO-consuming process, such as a gas fermentation process, with a CO 2  electrolysis process. The invention is capable of utilizing a CO 2 -comprising gaseous substrate generated by an industrial process and provides for one or more removal modules to remove at least one constituent from a CO 2 -comprising gaseous substrate prior to passage of the gaseous substrate to a CO 2  electrolysis module. The invention may further comprise one or more pressure modules, one or more CO 2  concentration modules, one or more O 2  separation modules, and/or an H 2  electrolysis module. Carbon conversion efficiency is increased by recycling CO 2  produced by a CO-consuming process to the CO 2  electrolysis process.

FIELD OF THE INVENTION

The invention relates to processes and methods for improving carbonconversion efficiency. In particular, the invention relates to thecombination of a carbon monoxide-consuming process with an industrialprocess, wherein gas from the industrial process undergoes treatment andconversion, and carbon dioxide produced by the carbon monoxide-consumingprocess is recycled to increase product yield.

BACKGROUND OF THE INVENTION

Carbon dioxide (CO₂) accounts for about 76% of global greenhouse gasemissions from human activities, with methane (16%), nitrous oxide (6%),and fluorinated gases (2%) accounting for the balance (United StatesEnvironmental Protection Agency). Reduction of greenhouse gas emissions,particularly CO₂, is critical to halt the progression of global warmingand the accompanying shifts in climate and weather.

It has long been recognized that catalytic processes, such as theFischer-Tropsch process, may be used to convert gases comprising CO₂,carbon monoxide (CO), and/or hydrogen (H₂) into a variety of fuels andchemicals. Recently, however, gas fermentation has emerged as analternative platform for the biological fixation of such gases. Inparticular, C1-fixing microorganisms have been demonstrated to convertgases comprising CO₂, CO, CH₄, and/or H₂ into products such as ethanoland 2,3-butanediol.

Such gases may be derived, for example, from industrial processes,including gas emissions from carbohydrate fermentation, gasfermentation, cement making, pulp and paper making, steel making, oilrefining and associated processes, petrochemical production, cokeproduction, anaerobic or aerobic digestion, gasification, natural gasextraction, oil extraction, metallurgical processes, production and/orrefinement of aluminum, copper, and/or ferroalloys, geologicalreservoirs, Fischer-Tropsch processes, methanol production, pyrolysis,steam methane reforming, dry methane reforming, partial oxidation ofbiogas or natural gas, and autothermal reforming of biogas or naturalgas.

To optimize the usage of these gases in CO-consuming processes, such asC1-fixing fermentation processes, an industrial gas may require acombination of treatment and conversion. Accordingly, there remains aneed for improved integration of industrial processes with CO-consumingprocesses, including processes for treatment and conversion ofindustrial gases, thereby optimizing carbon conversion efficiency.

BRIEF SUMMARY OF THE INVENTION

It is against the above background that the present invention providescertain advantages and advancements over the prior art.

Although this invention disclosed herein is not limited to specificadvantages or functionalities, the invention provides a process forimproving carbon conversion efficiency, wherein the process comprisespassing a CO₂-comprising gaseous substrate from an industrial process toa first removal module for removal of at least one constituent from theCO₂-comprising gaseous substrate to produce a first CO₂-treated gasstream, passing the first CO₂-treated gas stream to a CO₂ electrolysismodule for conversion of at least a portion of the first CO₂-treated gasstream to produce a CO-enriched stream and a first O₂-enriched stream,and passing at least a portion of the CO-enriched stream to aCO-consuming process.

In some aspects of the process described herein, the CO₂-comprisinggaseous substrate from the industrial process is first passed to apressure module to produce a pressurized CO₂-comprising gas stream, andthe pressurized CO₂-comprising gas stream is passed to the first removalmodule.

In some aspects of the process described herein, the process furthercomprises one or more of passing at least a portion of the firstO₂-enriched stream directly to the industrial process and passing atleast a portion of the first O₂-enriched stream to an O₂ separationmodule to produce a second O₂-enriched stream and an O₂-lean stream.

In some aspects of the process described herein, the process furthercomprises one or more of passing at least of portion of the secondO₂-enriched stream to the industrial process, passing at least ofportion of the O₂-lean stream to the CO₂ electrolysis module, andpassing at least of portion of the O₂-lean stream to the CO-consumingprocess.

In some aspects of the process described herein, the process furthercomprises passing at least a portion of the CO₂-comprising gaseoussubstrate from the industrial process and/or at least a portion of thefirst CO₂-treated gas stream to a first CO₂ concentration module toproduce a first CO₂-concentrated stream and a first CO₂-lean stream.

In some aspects of the process described herein, the process furthercomprises passing at least a portion of the first CO₂-concentratedstream to one or more of the first removal module and the CO₂electrolysis module.

In some aspects of the process described herein, the first CO₂-leanstream comprises CO and/or H₂, and the process further comprises passingat least a portion of the first CO₂-lean stream to the CO-consumingprocess.

In some aspects of the process described herein, the process comprisespassing at least a portion of the CO-enriched stream to a pressuremodule to produce a pressurized CO-stream and passing at least a portionof the pressurized CO-stream to the CO-consuming process.

In some aspects of the process described herein, the process furthercomprises passing a water substrate to an H₂ electrolysis module toproduce an H₂-enriched stream and passing at least a portion of theH₂-enriched stream to the CO-consuming process.

In some aspects of the process described herein, the CO-consumingprocess produces a tail gas comprising CO₂.

In some aspects of the process described herein, the process furthercomprises one or more of passing at least a portion of the tail gascomprising CO₂ to the first removal module or to a second removal modulefor removal of at least one constituent from the tail gas to produce asecond CO₂-treated gas stream and passing at least a portion of the tailgas comprising CO₂ to a second CO₂ concentration module to produce asecond CO₂-concentrated stream and a second CO₂-lean stream.

In some aspects of the process described herein, at least a portion ofthe tail gas comprising CO₂ is passed to a pressure module to produce apressurized tail gas stream, and the pressurized tail gas stream ispassed to the first removal module and/or the second removal module.

In some aspects of the process described herein, the process furthercomprises passing at least a portion of the second CO₂-concentratedstream to the first removal module or to the second removal module forremoval of at least one constituent from the tail gas to produce asecond CO₂-treated gas stream.

In some aspects of the process described herein, the process furthercomprises passing at least a portion of the second CO₂-treated gasstream to the CO₂ electrolysis module.

In some aspects of the process described herein, the CO₂-comprisinggaseous substrate from the industrial process further comprises one ormore of CO, H₂, and CH₄.

In some aspects of the process described herein, the industrial processis selected from the group comprising carbohydrate fermentation, gasfermentation, cement making, pulp and paper making, steel making, oilrefining and associated processes, petrochemical production, cokeproduction, anaerobic or aerobic digestion, gasification, natural gasextraction, oil extraction, metallurgical processes, production and/orrefinement of aluminum, copper, and/or ferroalloys, geologicalreservoirs, Fischer-Tropsch processes, methanol production, pyrolysis,steam methane reforming, dry methane reforming, partial oxidation ofbiogas or natural gas, and autothermal reforming of biogas or naturalgas.

In some aspects of the process described herein, the CO₂-comprisinggaseous substrate is derived from a blend of at least two or moresources.

In some aspects of the process described herein, the first removalmodule is selected from the group consisting of a hydrolysis module, anacid gas removal module, a deoxygenation module, a catalytichydrogenation module, a particulate removal module, a chloride removalmodule, a tar removal module, and a hydrogen cyanide polishing module.

In some aspects of the process described herein, at least oneconstituent removed from the CO₂-comprising gas substrate is selectedfrom the group consisting of sulfur compounds, aromatic compounds,alkynes, alkenes, alkanes, olefins, nitrogen compounds, oxygen,phosphorous-comprising compounds, particulate matter, solids, oxygen,halogenated compounds, silicon-comprising compounds, carbonyls, metals,alcohols, esters, ketones, peroxides, aldehydes, ethers, tars, andnaphthalene.

In some aspects of the process described herein, the CO-consumingprocess is a fermentation process comprising a culture of at least onecarboxydotrophic microorganism. The carboxydotrophic microorganism maybe a carboxydotrophic bacterium.

In some aspects of the process described herein, the carboxydotrophicbacterium is selected from the group comprising Moorella, Clostridium,Ruminococcus, Acetobacterium, Eubacterium, Butyribacterium, Oxobacter,Methanosarcina, and Desulfotomaculum. In some aspects of the processdescribed herein, the carboxydotrophic bacterium is Clostridiumautoethanogenum.

In some aspects of the process described herein, the fermentationprocess produces a fermentation product selected from the groupconsisting of ethanol, butyrate, 2,3-butanediol, lactate, butene,butadiene, methyl ethyl ketone, ethylene, acetone, isopropanol, lipids,3-hydroypropionate, terpenes, fatty acids, 2-butanol, 1,2-propanediol,and 1-propanol.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, and 1C show a process integration scheme depictingintegration of a removal module, a CO₂ electrolysis module, and anoptional H₂ electrolysis module with a CO-consuming process. FIG. 1Bfurther shows a pressure module prior to a removal module. FIG. 1Cfurther shows a pressure module prior to a CO-consuming process.

FIG. 2 shows a process integration scheme depicting integration of aremoval module, a CO₂ electrolysis module, an optional O₂ separationmodule, and an optional H₂ electrolysis module with a CO-consumingprocess.

FIG. 3 shows a process integration scheme depicting integration of anoptional CO₂ concentration module prior to a removal module, a CO₂electrolysis module, an optional H₂ electrolysis module, and an optionalO₂ separation module with a CO-consuming process.

FIG. 4 shows a process integration scheme depicting integration of anoptional CO₂ concentration module following a removal module, a CO₂electrolysis module, an optional H₂ electrolysis module, and an optionalO₂ separation module with a CO-consuming process.

FIG. 5 shows a process integration scheme depicting integration of an H₂electrolysis module following an optional pressure module, wherein aportion of the gas from the H₂ electrolysis module is blended with thegas from the CO₂ electrolysis module prior to being passed to theCO-consuming process.

FIG. 6 shows a process integration scheme depicting integration of afurther removal module following a CO₂ electrolysis module.

DETAILED DESCRIPTION OF THE INVENTION

The inventors have identified that the integration of a CO₂-generatingindustrial process with a CO-consuming process, as well as a removalprocess prior to a CO₂ electrolysis process, is capable of providingsubstantial benefits to the CO₂-generating industrial process and theCO-consuming process, which may be a C1-fixing fermentation process.

The term “industrial process” refers to a process for producing,converting, refining, reforming, extracting, or oxidizing a substanceinvolving chemical, physical, electrical, and/or mechanical steps.Exemplary industrial processes include, but are not limited to,carbohydrate fermentation, gas fermentation, cement making, pulp andpaper making, steel making, oil refining and associated processes,petrochemical production, coke production, anaerobic or aerobicdigestion, gasification (such as gasification of biomass, liquid wastestreams, solid waste streams, municipal streams, fossil resourcesincluding natural gas, coal and oil), natural gas extraction, oilextraction, metallurgical processes, production and/or refinement ofaluminum, copper, and/or ferroalloys, geological reservoirs,Fischer-Tropsch processes, methanol production, pyrolysis, steam methanereforming, dry methane reforming, partial oxidation of biogas or naturalgas, and autothermal reforming of biogas or natural gas. In theseembodiments, the substrate and/or C1-carbon source may be captured fromthe industrial process before it is emitted into the atmosphere, usingany convenient method.

The terms “gas from an industrial process,” “gas source from anindustrial process,” and “gaseous substrate from an industrial process”can be used interchangeably to refer to an off-gas from an industrialprocess, a by-product of an industrial process, a co-product of anindustrial process, a gas recycled within an industrial process, and/ora gas used within an industrial facility for energy recovery. In someembodiments, a gas from an industrial process is a pressure swingadsorption (PSA) tail gas. In some embodiments, a gas from an industrialprocess is a gas obtained through a CO₂ extraction process, which mayinvolve amine scrubbing or use of a carbonic anhydrase solution.

“C1” refers to a one-carbon molecule, for example, CO, CO₂, methane(CH₄), or methanol (CH₃OH). “C1-oxygenate” refers to a one-carbonmolecule that also comprises at least one oxygen atom, for example, CO,CO₂, or CH₃OH. “C1-carbon source” refers a one carbon-molecule thatserves as a partial or sole carbon source for a microorganism of theinvention. For example, a C1-carbon source may comprise one or more ofCO, CO₂, CH₄, CH₃OH, or formic acid (CH₂O₂). Preferably, a C1-carbonsource comprises one or both of CO and CO₂. A “C1-fixing microorganism”is a microorganism that has the ability to produce one or more productsfrom a C1-carbon source. Typically, a microorganism of the invention isa C1-fixing bacterium.

“Substrate” refers to a carbon and/or energy source. Typically, thesubstrate is gaseous and comprises a C1-carbon source, for example, CO,CO₂, and/or CH₄. Preferably, the substrate comprises a C1-carbon sourceof CO or CO and CO₂. The substrate may further comprise other non-carboncomponents, such as H₂, N₂, or electrons. As used herein, “substrate”may refer to a carbon and/or energy source for a microorganism of theinvention.

The term “co-substrate” refers to a substance that, while notnecessarily being the primary energy and material source for productsynthesis, can be utilised for product synthesis when combined withanother substrate, such as the primary substrate.

A “CO₂-comprising gaseous substrate,” “CO₂-comprising gas,” or“CO₂-comprising gaseous source” may include any gas that comprises CO₂.The gaseous substrate will typically comprise a significant proportionof CO₂, preferably at least about 5% to about 100% CO₂ by volume.Additionally, the gaseous substrate may comprise one or more of hydrogen(H₂), oxygen (O₂), nitrogen (N₂), and/or CH₄. As used herein, CO, H₂,and CH₄ may be referred to as “energy-rich gases.”

The term “carbon capture” as used herein refers to the sequestration ofcarbon compounds including CO₂ and/or CO from a stream comprising CO₂and/or CO and either a) converting the CO₂ and/or CO into products, b)converting the CO₂ and/or CO into substances suitable for long termstorage, c) trapping the CO₂ and/or CO in substances suitable for longterm storage, or d) a combination of these processes.

The terms “increasing the efficiency,” “increased efficiency,” and thelike refer to an increase in the rate and/or output of a reaction, suchas an increased rate of converting the CO₂ and/or CO into productsand/or an increased product concentration. When used in relation to afermentation process, “increasing the efficiency” includes, but is notlimited to, increasing one or more of the rate of growth ofmicroorganisms catalysing a fermentation, the growth and/or productproduction rate at elevated product concentrations, the volume ofdesired product produced per volume of substrate consumed, the rate ofproduction or level of production of the desired product, and therelative proportion of the desired product produced compared with otherby-products of the fermentation.

“Reactant” as used herein refers to a substance that is present in achemical reaction and is consumed during the reaction to produce aproduct. A reactant is a starting material that undergoes a changeduring a chemical reaction. In particular embodiments, a reactantincludes, but is not limited to, CO and/or H₂. In particularembodiments, a reactant is CO₂.

A “CO-consuming process” refers to a process wherein CO is a reactant;CO is consumed to produce a product. A non-limiting example of aCO-consuming process is a C1-fixing gas fermentation process. ACO-consuming process may involve a CO₂-producing reaction. For example,a CO-consuming process may result in the production of at least oneproduct, such as a fermentation product, as well as CO₂. In anotherexample, acetic acid production is a CO-consuming process, wherein CO isreacted with methanol under pressure.

“Gas stream” refers to any stream of substrate which is capable of beingpassed, for example, from one module to another, from one module to aCO-consuming process, and/or from one module to a carbon capture means.

Gas streams typically will not be a pure CO₂ stream and will compriseproportions of at least one other component. For instance, each sourcemay have differing proportions of CO₂, CO, H₂, and various constituents.Due to the varying proportions, a gas stream must be processed prior tobeing introduced to a CO-consuming process. Processing of the gas streamincludes the removal and/or conversion of various constituents that maybe microbe inhibitors and/or catalyst inhibitors. Preferably, catalystinhibitors are removed and/or converted prior to being passed to anelectrolysis module, and microbe inhibitors are removed and/or convertedprior to being passed to a CO-consuming process. Additionally, a gasstream may need to undergo one or more concentration steps whereby theconcentration of CO and/or CO₂ is increased. Preferably, a gas streamwill undergo a concentration step to increase the concentration of CO₂prior to being passed to the electrolysis module. It has been found thathigher concentrations of CO₂ being passing into the electrolysis moduleresults in higher concentrations of CO coming out of the electrolysismodule.

“Removal module,” “contaminant removal module,” “clean-up module,”“processing module,” and the like include technologies that are capableof either converting and/or removing at least one constituent from a gasstream. Non-limiting examples of removal modules include hydrolysismodules, acid gas removal modules, deoxygenation modules, catalytichydrogenation modules, particulate removal modules, chloride removalmodules, tar removal modules, and hydrogen cyanide polishing modules.

The terms “constituents,” “contaminants,” and the like, as used herein,refer to the microbe inhibitors and/or catalyst inhibitors that may befound in a gas stream. In particular embodiments, the constituentsinclude, but are not limited to, sulfur compounds, aromatic compounds,alkynes, alkenes, alkanes, olefins, nitrogen compounds,phosphorous-comprising compounds, particulate matter, solids, oxygen,halogenated compounds, silicon-comprising compounds, carbonyls, metals,alcohols, esters, ketones, peroxides, aldehydes, ethers, tars, andnapthalene. Preferably, the constituent removed by the removal moduledoes not include CO₂.

“Microbe inhibitors” as used herein refer to one or more constituentsthat slow down or prevent a particular chemical reaction or otherprocess, including the microbe. In particular embodiments, the microbeinhibitors include, but are not limited to, oxygen (O₂), hydrogencyanide (HCN), acetylene (C₂H₂), and BTEX (benzene, toluene, ethylbenzene, xylene).

“Catalyst inhibitor,” “adsorbent inhibitor,” and the like, as usedherein, refer to one or more substances that decrease the rate of orprevent a chemical reaction. In particular embodiments, the catalystinhibitors may include, but are not limited to, hydrogen sulfide (H₂S)and carbonyl sulfide (COS).

In certain instances, at least one constituent removed is produced,introduced, and/or concentrated by a fermentation step. One or more ofthese constituents may be present in a post-fermentation gaseoussubstrate. For example, sulfur, in the form of H₂S may be produced,introduced, and/or concentrated by a fermentation step. In particularembodiments, hydrogen sulfide is introduced in the fermentation step. Invarious embodiments, the post-fermentation gaseous substrate comprisesat least a portion of hydrogen sulfide. Hydrogen sulfide may be acatalyst inhibitor. As such, the hydrogen sulfide may be inhibiting toparticular electrolysis modules. In order to pass a non-inhibitingpost-fermentation gaseous substrate to the electrolyzer, at least aportion of the hydrogen sulfide, or other constituent present in thepost-fermentation gaseous substrate, may need to be removed by one ormore removal module. In another embodiment, acetone may be produced by afermentation step, and charcoal may be used as a removal module.

The terms “treated gas” and “treated gas stream” refer to a gas streamthat has been passed through at least one removal module and has had oneor more constituent removed and/or converted. For example, a“CO₂-treated gas stream” refers to a CO₂-comprising gas that has passedthrough one or more removal module.

“Concentration module” and the like refer to technology capable ofincreasing the level of a particular component in a gas stream. Inparticular embodiments, the concentration module is a CO₂ concentrationmodule, wherein the proportion of CO₂ in the gas stream leaving the CO₂concentration module is higher relative to the proportion of CO₂ in thegas stream prior to being passed to the CO₂ concentration module. Insome embodiments, a CO₂ concentration module uses deoxygenationtechnology to remove O₂ from a gas stream and thus increase theproportion of CO₂ in the gas stream. In some embodiments, a CO₂concentration module uses pressure swing adsorption (PSA) technology toremove H₂ from a gas stream and thus increase the proportion of CO₂ inthe gas stream. In certain instances, a fermentation process performsthe function of a CO₂ concentration module. In some embodiments, a gasstream from a concentration module is passed to a carbon capture andsequestration (CCS) unit or an enhanced oil recovery (EOR) unit.

The terms “electrolysis module” and “electrolyzer” can be usedinterchangeably to refer to a unit that uses electricity to drive anon-spontaneous reaction. Electrolysis technologies are known in theart. Exemplary processes include alkaline water electrolysis, proton oranion exchange membrane (PEM, AEM) electrolysis, and solid oxideelectrolysis (SOE) (Ursua et al., Proceedings of the IEEE100(2):410-426, 2012; Jhong et al., Current Opinion in ChemicalEngineering 2:191-199, 2013). The term “faradaic efficiency” is a valuethat references the number of electrons flowing through an electrolyzerand being transferred to a reduced product rather than to an unrelatedprocess. SOE modules operate at elevated temperatures. Below thethermoneutral voltage of an electrolysis module, an electrolysisreaction is endothermic. Above the thermoneutral voltage of anelectrolysis module, an electrolysis reaction is exothermic. In someembodiments, an electrolysis module is operated without added pressure.In some embodiments, an electrolysis module is operated at a pressure of5-10 bar.

A “CO₂ electrolysis module” refers to a unit capable of splitting CO₂into CO and O₂ and is defined by the following stoichiometric reaction:2CO₂+electricity→2CO+O₂. The use of different catalysts for CO₂reduction impact the end product. Catalysts including, but not limitedto, Au, Ag, Zn, Pd, and Ga catalysts, have been shown effective for theproduction of CO from CO₂. In some embodiments, the pressure of a gasstream leaving a CO₂ electrolysis module is approximately 5-7 barg.

“H₂ electrolysis module,” “water electrolysis module,” and “H₂Oelectrolysis module” refer to a unit capable of splitting H₂O, in theform of steam, into H₂ and O₂ and is defined by the followingstoichiometric reaction: 2H₂O+electricity→2H₂+O₂. An H₂O electrolysismodule reduces protons to H₂ and oxidizes O²⁻ to O₂. H₂ produced byelectrolysis can be blended with a C1-comprising gaseous substrate as ameans to supply additional feedstock and to improve substratecomposition.

H₂ and CO₂ electrolysis modules have 2 gas outlets. One side of theelectrolysis module, the anode, comprises H₂ or CO (and other gases suchas unreacted water vapor or unreacted CO₂). The second side, thecathode, comprises O₂ (and potentially other gases). The composition ofa feedstock being passed to an electrolysis process may determine thepresence of various components in a CO stream. For instance, thepresence of inert components, such as CH₄ and/or N₂, in a feedstock mayresult in one or more of those components being present in theCO-enriched stream. Additionally, in some electrolyzers, O₂ produced atthe cathode crosses over to the anode side where CO is generated and/orCO crosses over to the anode side, leading to cross contamination of thedesired gas products.

The term “separation module” is used to refer to a technology capable ofdividing a substance into two or more components. For example, an “O₂separation module” may be used to separate an O₂-comprising gaseoussubstrate into a stream comprising primarily O₂ (also referred to as an“O₂-enriched stream” or “O₂-rich gas”) and a stream that does notprimarily comprise O₂, comprises no O₂, or comprises only trace amountsof O₂ (also referred to as an “O₂-lean stream” or “O₂-depleted stream”).

As used herein, the terms “enriched stream,” “rich gas,” “high puritygas,” and the like refer to a gas stream having a greater proportion ofa particular component following passage through a module, such as anelectrolysis module, as compared to the proportion of the component inthe input stream into the module. For example, a “CO-enriched stream”may be produced upon passage of a CO₂-comprising gaseous substratethrough a CO₂ electrolysis module. An “H₂-enriched stream” may beproduced upon passage of a water gaseous substrate through an H₂electrolysis module. An “O₂-enriched stream” emerges automatically fromthe anode of a CO₂ or H₂ electrolysis module; an “O₂-enriched stream”may also be produced upon passage of an O₂-comprising gaseous substratethrough an O₂ separation module. A “CO₂-enriched stream” may be producedupon passage of a CO₂-comprising gaseous substrate through a CO₂concentration module.

As used herein, the terms “lean stream,” “depleted gas,” and the likerefer to a gas stream having a lesser proportion of a particularcomponent following passage through a module, such as a concentrationmodule or a separation module, as compared to the proportion of thecomponent in the input stream into the module. For example, an O₂-leanstream may be produced upon passage of an O₂-comprising gaseoussubstrate through an O₂ separation module. The O₂-lean stream maycomprise unreacted CO₂ from a CO₂ electrolysis module. The O₂-leanstream may comprise trace amounts of O₂ or no O₂. A “CO₂-lean stream”may be produced upon passage of a CO₂-comprising gaseous substratethrough a CO₂ concentration module. The CO₂-lean stream may comprise CO,H₂, and/or a constituent such as a microbe inhibitor or a catalystinhibitor. The CO₂-lean stream may comprise trace amounts of CO₂ or noCO₂.

In particular embodiments, the invention provides an integrated processwherein the pressure of the gas stream is capable of being increasedand/or decreased. The term “pressure module” refers to a technologycapable of producing (i.e., increasing) or decreasing the pressure of agas stream. The pressure of the gas may be increased and/or decreasedthrough any suitable means, for example one or more compressor and/orvalve. In certain instances, a gas stream may have a lower than optimumpressure, or the pressure of the gas stream may be higher than optimal,and thus, a valve may be included to reduce the pressure. A pressuremodule may be located before or after any module described herein. Forexample, a pressure module may be utilized prior to a removal module,prior to a concentration module, prior to an electrolysis module, and/orprior to a CO-consuming process.

A “pressurized gas stream” refers to a gaseous substrate that has passedthrough a pressure module. A “pressurized gas stream” may also be usedto refer to a gas stream that meets the operating pressure requirementsof a particular module.

The terms “post-CO-consuming process gaseous substrate,”“post-CO-consuming process tail gas,” “tail gas,” and the like may beused interchangeably to refer to a gas that has passed through aCO-consuming process. The post-CO-consuming process gaseous substratemay comprise unreacted CO, unreacted H₂, and/or CO₂ produced (or nottaken up in parallel) by the CO-consuming process. The post-CO-consumingprocess gaseous substrate may further be passed to one or more of apressure module, a removal module, a CO₂ concentration module, and/or anelectrolysis module. In some embodiments, a “post-CO-consuming processgaseous substrate” is a post-fermentation gaseous substrate.

The term “desired composition” is used to refer to the desired level andtypes of components in a substance, such as, for example, of a gasstream. More particularly, a gas is considered to have a “desiredcomposition” if it contains a particular component (i.e., CO, H₂, and/orCO₂) and/or contains a particular component at a particular proportionand/or does not comprise a particular component (i.e., a contaminantharmful to the microorganisms) and/or does not comprise a particularcomponent at a particular proportion. More than one component may beconsidered when determining whether a gas stream has a desiredcomposition.

While it is not necessary for the substrate to comprise any H₂, thepresence of H₂ should not be detrimental to product formation inaccordance with methods of the invention. In particular embodiments, thepresence of H₂ results in an improved overall efficiency of alcoholproduction. In one embodiment, the substrate comprises about 30% or lessH₂ by volume, 20% or less H₂ by volume, about 15% or less H₂ by volumeor about 10% or less H₂ by volume. In other embodiments, the substratestream comprises low concentrations of H₂, for example, less than 5%, orless than 4%, or less than 3%, or less than 2%, or less than 1%, or issubstantially H₂ free.

The substrate may also comprise some CO for example, such as about 1% toabout 80% CO by volume, or 1% to about 30% CO by volume. In oneembodiment, the substrate comprises less than or equal to about 20% COby volume. In particular embodiments, the substrate comprises less thanor equal to about 15% CO by volume, less than or equal to about 10% COby volume, less than or equal to about 5% CO by volume or substantiallyno CO.

Substrate composition can be improved to provide a desired or optimumH₂:CO:CO₂ ratio. The desired H₂:CO:CO₂ ratio is dependent on the desiredfermentation product of the fermentation process. For ethanol, theoptimum H₂:CO:CO₂ ratio would be:

${(x)\text{:}(y)\text{:}( \frac{x - {2y}}{3} )},$

where x>2y, in order to satisfy the stoichiometry for ethanolproduction:

$ {{(x)H_{2}} + {(y){CO}} + {( \frac{x - {2y}}{3} ){CO}_{2}}}arrow{{( \frac{x + y}{6} )C_{2}H_{5}{OH}} + {( \frac{x - y}{2} )H_{2}{O.}}} $

Operating the fermentation process in the presence of H₂ has the addedbenefit of reducing the amount of CO₂ produced by the fermentationprocess. For example, a gaseous substrate comprising minimal H₂ willtypically produce ethanol and CO₂ by the following stoichiometry:6CO+3H₂O→C₂H₅OH+4CO₂. As the amount of H₂ utilized by the C1 fixingbacterium increase, the amount of CO₂ produced decreases, i.e.,2CO+4H₂→C₂H₅OH+H₂O.

When CO is the sole carbon and energy source for ethanol production, aportion of the carbon is lost to CO₂ as follows:

6CO+3H₂O→C₂H₅OH+4CO₂(ΔG°=−224.90 kJ/mol ethanol)

As the amount of H₂ available in the substrate increases, the amount ofCO₂ produced decreases. At a stoichiometric ratio of 1:2 (CO/H₂), CO₂production is completely avoided.

5CO+1H₂+2H₂O→1C₂H₅OH+3CO₂(ΔG°=−204.80 kJ/mol ethanol)

4CO+2H₂+1H₂O→C₂H₅OH+2CO₂(ΔG°=−184.70 kJ/mol ethanol)

3CO+3H₂→1C₂H₅OH+1CO₂(ΔG°=−164.60 kJ/mol ethanol)

The composition of the substrate may have a significant impact on theefficiency and/or cost of the reaction. For example, the presence of O₂may reduce the efficiency of an anaerobic fermentation process.Depending on the composition of the substrate, it may be desirable totreat, scrub, or filter the substrate to remove any undesiredimpurities, such as toxins, undesired components, or dust particles,and/or increase the concentration of desirable components. Furthermore,carbon capture can be increased by recycling CO₂ produced by aCO-consuming process back to a CO₂ electrolysis module, therebyimproving yield of the CO-consuming process. CO₂ produced by theCO-consuming process may be treated prior to passage through the CO₂electrolysis module.

In some embodiments, a CO-consuming process is performed in abioreactor. The term “bioreactor” includes a fermentation deviceconsisting of one or more vessels and/or towers or piping arrangements,which includes the Continuous Stirred Tank Reactor (CSTR), ImmobilizedCell Reactor (ICR), Trickle Bed Reactor (TBR), Bubble Column, Gas LiftFermenter, Static Mixer, a circulated loop reactor, a membrane reactor,such as a Hollow Fibre Membrane Bioreactor (HFM BR) or other vessel orother device suitable for gas-liquid contact. The reactor is preferablyadapted to receive a gaseous substrate comprising CO, CO₂, H₂, ormixtures thereof. The reactor may comprise multiple reactors (stages),either in parallel or in series. For example, the reactor may comprise afirst growth reactor in which the bacteria are cultured and a secondfermentation reactor, to which fermentation broth from the growthreactor may be fed and in which most of the fermentation products may beproduced.

Operating a bioreactor at elevated pressures allows for an increasedrate of gas mass transfer from the gas phase to the liquid phase.Accordingly, it is generally preferable to perform theculture/fermentation at pressures higher than atmospheric pressure.Also, since a given gas conversion rate is, in part, a function of thesubstrate retention time and retention time dictates the required volumeof a bioreactor, the use of pressurized systems can greatly reduce thevolume of the bioreactor required and, consequently, the capital cost ofthe culture/fermentation equipment. This, in turn, means that theretention time, defined as the liquid volume in the bioreactor dividedby the input gas flow rate, can be reduced when bioreactors aremaintained at elevated pressure rather than atmospheric pressure. Theoptimum reaction conditions will depend partly on the particularmicroorganism used. However, in general, it is preferable to operate thefermentation at a pressure higher than atmospheric pressure. Also, sincea given gas conversion rate is in part a function of substrate retentiontime and achieving a desired retention time in turn dictates therequired volume of a bioreactor, the use of pressurized systems cangreatly reduce the volume of the bioreactor required, and consequentlythe capital cost of the fermentation equipment.

Unless the context requires otherwise, the phrases “fermenting,”“fermentation process,” “fermentation reaction” and the like, as usedherein, are intended to encompass both the growth phase and productbiosynthesis phase of the gaseous substrate. In certain embodiments, thefermentation is performed in the absence of carbohydrate substrates,such as sugar, starch, lignin, cellulose, or hemicellulose.

A culture is generally maintained in an aqueous culture medium thatcontains nutrients, vitamins, and/or minerals sufficient to permitgrowth of a microorganism. “Nutrient media,” “nutrient medium,” and“culture medium” are used to describe bacterial growth media.Preferably, the aqueous culture medium is an anaerobic microbial growthmedium, such as a minimal anaerobic microbial growth medium. Suitablemedia are well known in the art. The term “nutrient” includes anysubstance that may be utilised in a metabolic pathway of amicroorganism. Exemplary nutrients include potassium, B vitamins, tracemetals, and amino acids.

The terms “fermentation broth” and “broth” are intended to encompass themixture of components including nutrient media and a culture or one ormore microorganisms. It should be noted that the term microorganism andthe term bacteria are used interchangeably herein.

A microorganism of the invention may be cultured with a gas stream toproduce one or more products. For instance, a microorganism of theinvention may produce or may be engineered to produce ethanol (WO2007/117157), acetate (WO 2007/117157), butanol (WO 2008/115080 and WO2012/053905), butyrate (WO 2008/115080), 2,3-butanediol (WO 2009/151342and WO 2016/094334), lactate (WO 2011/112103), butene (WO 2012/024522),butadiene (WO 2012/024522), methyl ethyl ketone (2-butanone) (WO2012/024522 and WO 2013/185123), ethylene (WO 2012/026833), acetone (WO2012/115527), isopropanol (WO 2012/115527), lipids (WO 2013/036147),3-hydroxypropionate (3-HP) (WO 2013/180581), terpenes, includingisoprene (WO 2013/180584), fatty acids (WO 2013/191567), 2-butanol (WO2013/185123), 1,2-propanediol (WO 2014/036152), 1-propanol (WO2014/0369152), chorismate-derived products (WO 2016/191625),3-hydroxybutyrate (WO 2017/066498), and 1,3-butanediol (WO2017/0066498). In addition to one or more target products, amicroorganism of the invention may also produce ethanol, acetate, and/or2,3-butanediol. In certain embodiments, microbial biomass itself may beconsidered a product. These products may be further converted to produceat least one component of diesel, jet fuel, and/or gasoline.Additionally, the microbial biomass may be further processed to producea single cell protein (SCP).

A “microorganism” is a microscopic organism, especially a bacterium,archea, virus, or fungus. A microorganism of the invention is typicallya bacterium. As used herein, recitation of “microorganism” should betaken to encompass “bacterium.”

A “parental microorganism” is a microorganism used to generate amicroorganism of the invention. The parental microorganism may be anaturally-occurring microorganism (i.e., a wild-type microorganism) or amicroorganism that has been previously modified (i.e., a mutant orrecombinant microorganism). A microorganism of the invention may bemodified to express or overexpress one or more enzymes that were notexpressed or overexpressed in the parental microorganism. Similarly, amicroorganism of the invention may be modified to comprise one or moregenes that were not contained by the parental microorganism. Amicroorganism of the invention may also be modified to not express or toexpress lower amounts of one or more enzymes that were expressed in theparental microorganism. In one embodiment, the parental microorganism isClostridium autoethanogenum, Clostridium ljungdahlii, or Clostridiumragsdalei. In a preferred embodiment, the parental microorganism isClostridium autoethanogenum LZ1561, which was deposited on Jun. 7, 2010with Deutsche Sammlung von Mikroorganismen and Zellkulturen GmbH (DSMZ)located at InhoffenstraB 7B, D-38124 Braunschwieg, Germany on Jun. 7,2010 under the terms of the Budapest Treaty and accorded accessionnumber DSM23693. This strain is described in International PatentApplication No. PCT/NZ2011/000144, which published as WO 2012/015317.

The term “derived from” indicates that a nucleic acid, protein, ormicroorganism is modified or adapted from a different (i.e., a parentalor wild-type) nucleic acid, protein, or microorganism, so as to producea new nucleic acid, protein, or microorganism. Such modifications oradaptations typically include insertion, deletion, mutation, orsubstitution of nucleic acids or genes. Generally, a microorganism ofthe invention is derived from a parental microorganism. In oneembodiment, a microorganism of the invention is derived from Clostridiumautoethanogenum, Clostridium ljungdahlii, or Clostridium ragsdalei. In apreferred embodiment, a microorganism of the invention is derived fromClostridium autoethanogenum LZ1561, which is deposited under DSMZaccession number DSM23693.

A microorganism of the invention may be further classified based onfunctional characteristics. For example, the microorganism of theinvention may be or may be derived from a C1-fixing microorganism, ananaerobe, an acetogen, an ethanologen, a carboxydotroph, and/or amethanotroph.

“Wood-Ljungdahl” refers to the Wood-Ljungdahl pathway of carbon fixationas described, i.e., by Ragsdale, Biochim Biophys Acta, 1784: 1873-1898,2008. “Wood-Ljungdahl microorganisms” refers, predictably, tomicroorganisms comprising the Wood-Ljungdahl pathway. Generally, amicroorganism of the invention contains a native Wood-Ljungdahl pathway.Herein, a Wood-Ljungdahl pathway may be a native, unmodifiedWood-Ljungdahl pathway or it may be a Wood-Ljungdahl pathway with somedegree of genetic modification (i.e., overexpression, heterologousexpression, knockout, etc.) so long as it still functions to convert CO,CO₂, and/or H₂ to acetyl-CoA.

An “anaerobe” is a microorganism that does not require O₂ for growth. Ananaerobe may react negatively or even die if O₂ is present above acertain threshold. However, some anaerobes are capable of tolerating lowlevels of O₂ (i.e., 0.000001-5% O₂). Typically, a microorganism of theinvention is an anaerobe.

“Acetogens” are obligately anaerobic bacteria that use theWood-Ljungdahl pathway as their main mechanism for energy conservationand for synthesis of acetyl-CoA and acetyl-CoA-derived products, such asacetate (Ragsdale, Biochim Biophys Acta, 1784: 1873-1898, 2008). Inparticular, acetogens use the Wood-Ljungdahl pathway as a (1) mechanismfor the reductive synthesis of acetyl-CoA from CO₂, (2) terminalelectron-accepting, energy conserving process, (3) mechanism for thefixation (assimilation) of CO₂ in the synthesis of cell carbon (Drake,Acetogenic Prokaryotes, In: The Prokaryotes, 3rd edition, p. 354, NewYork, N.Y., 2006). All naturally occurring acetogens are C1-fixing,anaerobic, autotrophic, and non-methanotrophic. Typically, amicroorganism of the invention is an acetogen.

An “ethanologen” is a microorganism that produces or is capable ofproducing ethanol. Typically, a microorganism of the invention is anethanologen.

An “autotroph” is a microorganism capable of growing in the absence oforganic carbon. Instead, autotrophs use inorganic carbon sources, suchas CO and/or CO₂. Typically, a microorganism of the invention is anautotroph.

A “carboxydotroph” is a microorganism capable of utilizing CO as a solesource of carbon and energy. Typically, a microorganism of the inventionis a carboxydotroph.

A “methanotroph” is a microorganism capable of utilizing methane as asole source of carbon and energy. In certain embodiments, amicroorganism of the invention is a methanotroph or is derived from amethanotroph. In other embodiments, a microorganism of the invention isnot a methanotroph or is not derived from a methanotroph.

Table 1 provides a representative list of microorganisms and identifiestheir functional characteristics

TABLE 1 Wood-Ljungdahl C1-fixing Anaerobe Acetogen Ethanologen AutotrophCarboxydotroph Acetobacterium woodii + + + + +/− ¹ + − Alkalibaculumbacchii + + + + + + + Blautia producta + + + + − + + Butyribacteriummethylotrophicum + + + + + + + Clostridium aceticum + + + + − + +Clostridium autoethanogenum + + + + + + + Clostridiumcarboxidivorans + + + + + + + Clostridium coskatii + + + + + + +Clostridium drakei + + + + − + + Clostridium formicoaceticum + + + +− + + Clostridium ljungdahlii + + + + + + + Clostridium magnum + + + +− + +/− ² Clostridium ragsdalei + + + + + + + Clostridiumscatologenes + + + + − + + Eubacterium limosum + + + + − + + Moorellathermautotrophica + + + + + + + Moorella thermoacetica (formerly + + + +  − ³ + + Clostridium thermoaceticum) Oxobacter pfennigii + + + + − + +Sporomusa ovata + + + + − + +/− ⁴ Sporomusa silvacetica + + + + − + +/−⁵ Sporomusa sphaeroides + + + + − + +/− ⁶ Thermoanaerobacterkiuvi + + + + − + − ¹ Acetobacterium woodi can produce ethanol fromfructose, but not from gas. ² It has not been investigated whetherClostridium magnum can grow on CO. ³ One strain of Moorellathermoacetica, Moorella sp. HUC22-1, has been reported to produceethanol from gas. ⁴ It has not been investigated whether Sporomusa ovatacan grow on CO. ⁵ It has not been investigated whether Sporomusasilvacetica can grow on CO. ⁶ It has not been investigated whetherSporomusa sphaeroides can grow on CO.

A “native product” is a product produced by a genetically unmodifiedmicroorganism. For example, ethanol, acetate, and 2,3-butanediol arenative products of Clostridium autoethanogenum, Clostridium ljungdahlii,and Clostridium ragsdalei. A “non-native product” is a product that isproduced by a genetically modified microorganism but is not produced bya genetically unmodified microorganism from which the geneticallymodified microorganism is derived.

“Selectivity” refers to the ratio of the production of a target productto the production of all fermentation products produced by amicroorganism. A microorganism of the invention may be engineered toproduce products at a certain selectivity or at a minimum selectivity.In one embodiment, a target product account for at least about 5%, 10%,15%, 20%, 30%, 50%, or 75% of all fermentation products produced by amicroorganism of the invention. In one embodiment, the target productaccounts for at least 10% of all fermentation products produced by amicroorganism of the invention, such that a microorganism of theinvention has a selectivity for the target product of at least 10%. Inanother embodiment, the target product accounts for at least 30% of allfermentation products produced by a microorganism of the invention, suchthat a microorganism of the invention has a selectivity for the targetproduct of at least 30%.

A culture/fermentation should desirably be carried out under appropriateconditions for production of the target product. Typically, theculture/fermentation is performed under anaerobic conditions. Reactionconditions to consider include pressure (or partial pressure),temperature, gas flow rate, liquid flow rate, media pH, media redoxpotential, agitation rate (if using a continuous stirred tank reactor),inoculum level, maximum gas substrate concentrations to ensure that gasin the liquid phase does not become limiting, and maximum productconcentrations to avoid product inhibition. In particular, the rate ofintroduction of the substrate may be controlled to ensure that theconcentration of gas in the liquid phase does not become limiting, sinceproducts may be consumed by the culture under gas-limited conditions.

Target products may be separated or purified from a fermentation brothusing any method or combination of methods known in the art, including,for example, fractional distillation, evaporation, pervaporation, gasstripping, phase separation, and extractive fermentation, including forexample, liquid-liquid extraction. In certain embodiments, targetproducts are recovered from the fermentation broth by continuouslyremoving a portion of the broth from the bioreactor, separatingmicrobial cells from the broth (conveniently by filtration), andrecovering one or more target products from the broth. Alcohols and/oracetone may be recovered, for example, by distillation. Acids may berecovered, for example, by adsorption on activated charcoal. Separatedmicrobial cells are preferably returned to the bioreactor. The cell-freepermeate remaining after target products have been removed is alsopreferably returned to the bioreactor. Additional nutrients (such as Bvitamins) may be added to the cell-free permeate to replenish the mediumbefore it is returned to the bioreactor.

FIG. 1A shows a process for integration of an industrial process 110,one or more removal module 120, a CO₂ electrolysis process 130, anoptional H₂ electrolysis process 160, and a CO-consuming process 140.CO₂-comprising gas from an industrial process 110 is fed via a conduit112 to one or more removal module 120 to remove and/or convert one ormore constituent 128. The treated gas from the one or more removalmodule 120 is then fed via a conduit 122 to a CO₂ electrolysis module130 for conversion of at least a portion of the gas stream. In someembodiments, CO₂-comprising gas from the industrial process 110 isdirectly fed via a conduit 114 to the CO₂ electrolysis module 130 forconversion of at least a portion of the gas stream; in this embodiment,a constituent such as sulfur may be removed prior to passage through anindustrial process. Optionally, at least a portion of O₂ may be fed fromthe CO₂ electrolysis module 130 to the industrial process 110 via aconduit 136. At least a portion of the converted gas stream is passed,via a conduit 132, from the CO₂ electrolysis module 130 to aCO-consuming process 140. In some embodiments, a water substrate is fedvia a conduit 162 to an H₂ electrolysis module 160 for conversion of atleast a portion of the water substrate, and an H₂-enriched stream ispassed via a conduit 164 to the CO-consuming process 140. Optionally, atleast a portion of O₂ may be fed from the H₂ electrolysis module 160 tothe industrial process 110 via a conduit 166. The CO-consuming process140 produces at least one product 146 and a post-CO-consuming processgaseous substrate.

The CO-consuming process 140 of FIG. 1A may be a gas fermentationprocess and may occur in an inoculator and/or one or more bioreactors.For example, the CO-consuming process 140 may be a gas fermentationprocess in a bioreactor comprising a culture of at least one C1-fixingmicroorganism. In embodiments wherein the CO-consuming process 140 is agas fermentation process, a culture may be fermented to produce one ormore fermentation products 146 and a post-fermentation gaseous substrate(CO-consuming process gaseous substrate).

In some embodiments, the CO-consuming process 140 of FIG. 1A comprises aCO₂-producing reaction step. In embodiments wherein a post-CO-consumingprocess gaseous substrate comprises CO₂, at least a portion of thepost-CO-consuming process gaseous substrate is passed via a conduit 142to one or more removal module 150 to remove and/or convert one or moreconstituent 158. A treated gas stream comprising CO₂ is then passed viaa conduit 152 to a CO₂ electrolysis module 130 for conversion of atleast a portion of the gas stream. In particular embodiments, thepost-CO-consuming process gaseous substrate is passed via a conduit 142to the same one or more removal module 120 that receives CO₂-comprisinggas from the industrial process 110. In various embodiments, thepost-CO-consuming process gaseous substrate may be passed to the one ormore removal module 120 that receives the CO₂-comprising gas from theindustrial process 110 and the one or more removal module 150. Thisprocess of treating and electrolyzing the post-CO-consuming processgaseous substrate has been found to increase carbon capture efficiency.

In particular embodiments, at least one constituent removed by theremoval module 150 of FIG. 1A is produced, introduced, and/orconcentrated by the CO-consuming process 140, such as a gas fermentationprocess. In various embodiments, the one or more constituent produced,introduced, and/or concentrated by the fermentation step comprisessulfur. In certain instances, sulfur, such as hydrogen sulfide, isintroduced to the CO-consuming process 140. This sulfur was found toreduce the efficiency of the CO₂ electrolysis module 130. The removalmodule 150 was found to be successful at reducing the amount of sulfurin the post-CO-consuming process gaseous substrate prior to thepost-CO-consuming process gaseous substrate being passed to the CO₂electrolysis module 130. The use of the removal module 150 prior to theCO₂ electrolysis module 130 was found to increase the efficiency of theCO₂ electrolysis module 130.

The inventors have identified that the O₂ by-product of CO₂ and H₂electrolysis processes can provide additional benefits for theC1-generating industrial process. While fermentation processes of thecurrent invention are anaerobic processes, the inventors have identifiedthat the O₂ by-product of the CO production process, such as O₂ passedthrough conduit 136 in of FIG. 1A, can be used in a C1-generatingindustrial process. The high-purity O₂ by-product of the CO₂electrolysis process can be integrated with the industrial process andbeneficially offset costs, and in some cases, have synergy that furtherreduces costs for both the industrial process as well as the subsequentgas fermentation.

Typically, the industrial processes described herein derive the requiredO₂ by air separation. Production of O₂ by air separation is an energyintensive process which involves cryogenically separating O₂ from N₂ toachieve the highest purity. Production of O₂ by CO₂ and/or H₂electrolysis, and displacing O₂ produced by air separation, could offsetup to 5% of the electricity costs in an industrial process.

Several C1-generating industrial processes involving partial oxidationreactions require an O₂ input. Exemplary industrial processes includeBasic Oxygen Furnace (BOF) reactions, COREX or FINEX steel makingprocesses, Blast Furnace (BF) processes, ferroalloy productionprocesses, titanium dioxide production processes, and gasificationprocesses. Gasification processes include, but are not limited to,municipal solid waste gasification, biomass gasification, pet cokegasification, and coal gasification. In one or more of these industrialprocesses, O₂ from the CO₂ electrolysis process may be used to off-setor completely replace the O₂ typically supplied through air separation.

As shown in FIGS. 1B and 1C, a process for integration of an industrialprocess, one or more removal module, a CO₂ electrolysis process, anoptional H₂ electrolysis process, and a CO-consuming process may furthercomprise integration of one or more pressure module 170. For example, asshown in FIG. 1B, at least a portion of CO₂-comprising gas from anindustrial process 110 is fed via a conduit 112 to a pressure module 170to produce a pressurized CO₂-comprising gas stream. At least a portionof the pressurized CO₂-comprising gas stream is then passed via aconduit 172 to a removal module 120. At least a portion ofpost-CO-consuming process gaseous substrate may also be passed viaconduit 142 to a pressure module 170 to produce a pressurized tail gas.At least a portion of the pressurized tail gas is then passed via aconduit 172 to a removal module 150 and/or a removal module 120. Asshown in FIG. 1C, at least a portion of a converted gas stream ispassed, via a conduit 132, from a CO₂ electrolysis module 130 to apressure module 170 to produce a pressurized CO-comprising gas stream,which is passed via a conduit 172 to a CO-consuming process 140.

FIG. 2 shows a process for integration of an industrial process 210, aremoval module 220, a CO₂ electrolysis module 230, an optional H₂electrolysis process 270, a CO-consuming process 240, and an optional O₂separation module 260. CO₂-comprising gas from an industrial process 210is fed via a conduit 212 to one or more removal module 220 to removeand/or convert one or more constituent 228. The treated gas from the oneor more removal module 220 is then fed via a conduit 222 to a CO₂electrolysis module 230 for conversion of at least a portion of the gasstream. Optionally, at least a portion of O₂ may be fed from the CO₂electrolysis module 230 to the industrial process 210 via a conduit 236.At least a portion of the converted gas stream is passed from the CO₂electrolysis module 230 to the CO-consuming process 240 via a conduit232 to produce a product 246 and a post-CO-consuming process gaseoussubstrate. In some embodiments, a water substrate is fed via a conduit272 to an H₂ electrolysis module 270 for conversion of at least aportion of the water substrate, and an H₂-enriched stream is passed viaa conduit 274 to the CO-consuming process 240. Optionally, at least aportion of O₂ may be fed from the H₂ electrolysis module 270 to theindustrial process 210 via a conduit 276.

In particular embodiments, the process includes an O₂ separation module260 following the CO₂ electrolysis module 230 to separate at least aportion of O₂ from the gas stream. In embodiments utilizing an O₂separation module 260 after the CO₂ electrolysis module 230, at least aportion of the gas stream is fed from the CO₂ electrolysis module 230 tothe O₂ separation module 260, via a conduit 234. In embodimentsincorporating an O₂ separation module 260, at least a portion of O₂separated from the gas stream from the O₂ separation module 260(O₂-enriched stream) may be fed to the industrial process 210 via aconduit 264. In embodiments utilizing an O₂ separation module 260 afterthe CO₂ electrolysis module 230, at least a portion of the O₂-leanstream is fed from the O₂ separation module 260 to the CO-consumingprocess 240 via a conduit 262. In some embodiments utilizing an O₂separation module 260 after the CO₂ electrolysis module 230, at least aportion of the O₂-lean stream is fed from the O₂ separation module 260back to the CO₂ electrolysis module 230 via a conduit 266. Inembodiments not utilizing an O₂ separation module 260, a portion of thegas stream may be fed from the CO₂ electrolysis module 230 to theindustrial process 210 via a conduit 236.

In some embodiments, the CO-consuming process 240 of FIG. 2 comprises aCO₂-producing reaction step. In embodiments wherein thepost-CO-consuming process gaseous substrate comprises CO₂, at least aportion of the post-CO-consuming process gaseous substrate is passed viaa conduit 242 to one or more removal module 250 to remove and/or convertone or more constituent 258. A treated gas stream is then passed via aconduit 252 to a CO₂ electrolysis module 230 for conversion of at leasta portion of the gas stream. In particular embodiments, thepost-CO-consuming process gaseous substrate is passed via a conduit 242to the same one or more removal module 220 that receives theCO₂-comprising gas from the industrial process 210. In variousembodiments, the post-CO-consuming process gaseous substrate may bepassed to the one or more removal module 220 that receives theCO₂-comprising gas from the industrial process 210 and the one or moreremoval module 250.

The CO-consuming process 240 of FIG. 2 may be a gas fermentation processand may occur in an inoculator and/or one or more bioreactors. Forexample, the CO-consuming process 240 may be a gas fermentation processin a bioreactor comprising a culture of at least one C1-fixingmicroorganism. In embodiments wherein the CO-consuming process 240 is agas fermentation process, a culture may be fermented to produce one ormore fermentation products 246 and a post-fermentation gaseous substrate(post-CO-consuming process gaseous substrate).

The provision of a high purity CO₂ stream (CO₂-rich stream) to a CO₂electrolysis process has been found to increase the (carbon capture)efficiency of a CO-consuming process. To increase the concentration ofCO₂ in a stream, one or more CO₂ concentration module may beincorporated in the process. Preferably, the post electrolysis streamhas a concentration of CO between 20-90%.

FIG. 3 shows a process for integration of an industrial process 310 withan optional CO₂ concentration module 370, a removal module 320, a CO₂electrolysis module 330, an optional H₂ electrolysis module 380, aCO-consuming process 340, and an optional O₂ separation module 360, inaccordance with one aspect of the invention. In embodiments notincluding the CO₂ concentration module 370, CO₂-comprising gas from theindustrial process 310 is fed via a conduit 312 to a removal module 320.In embodiments including the CO₂ concentration module 370,CO₂-comprising gas from the industrial process 310 is fed via a conduit314 to a CO₂ concentration module 370 in order to increase theconcentration of CO₂ in the gas stream and to remove one or moreconstituent 374. The CO₂-concentrated gas stream is then fed via aconduit 372 to one or more removal module 320 to remove and/or convertone or more constituent 328. The treated gas from the one or moreremoval module 320 is then fed via a conduit 322 to a CO₂ electrolysismodule 330 for conversion of at least a portion of the gas stream. Atleast a portion of the converted gas stream is passed from the CO₂electrolysis module 330 to the CO-consuming process 340 via a conduit332. In some embodiments, the constituent 374 is CO and/or H₂, which ispassed via conduit 376 to the CO-consuming process 340. In someembodiments, a water substrate is fed via a conduit 382 to an H₂electrolysis module 380 for conversion of at least a portion of thewater substrate, and an H₂-enriched stream is passed via a conduit 384to the CO-consuming process 340. Optionally, at least a portion of O₂may be fed from the H₂ electrolysis module 380 to the industrial process310 via a conduit 386.

At least a portion of the gas stream from the CO₂ electrolysis module330 may be passed to the industrial process 310 via a conduit 336. Inparticular embodiments, the process includes an O₂ separation module 360following the CO₂ electrolysis module 330, where the gas stream ispassed from the CO₂ electrolysis module 330 to the O₂ separation module360 via a conduit 334 to separate at least a portion of O₂ from the gasstream. In embodiments utilizing an O₂ separation module 360 after theCO₂ electrolysis module 330, at least a portion of the removed O₂(O₂-enriched stream) is fed from the O₂ separation module 360 to theindustrial process 310 via a conduit 364. In embodiments utilizing an O₂separation module 360 after the CO₂ electrolysis module 330, at least aportion of the O₂-lean stream is fed from the O₂ separation module 360to the CO-consuming process 340 via a conduit 362. In some embodimentsutilizing an O₂ separation module 360 after the CO₂ electrolysis module330, at least a portion of the O₂-lean stream is fed from the O₂separation module 260 back to the CO₂ electrolysis module 330 via aconduit 366. In embodiments not utilizing an O₂ separation module 360, aportion of the gas stream may be fed from the CO₂ electrolysis module330 to the industrial process 310 via a conduit 336.

The process of concentrating the CO₂ in the gas stream prior to the oneor more removal modules 320 has been found to decrease undesired gases,thereby increasing the efficiency of a CO-consuming process, such as afermentation process. The amount of O₂ generated at the anode side of anelectrolysis module is 50% the amount of CO₂ produced at the cathode ofthe electrolysis module. The produced O₂ can be used to increase theefficiency of the industrial process 310, wherein at least a portion ofthe gas stream following electrolysis is passed to the industrialprocess 310.

In some embodiments, the CO-consuming process 340 of FIG. 3 comprises aCO₂-producing reaction step. In embodiments wherein thepost-CO-consuming process gaseous substrate comprises CO₂, thepost-CO-consuming process gaseous substrate is passed via a conduit 342to one or more removal module 350 to remove and/or convert one or moreconstituent 358. The treated gas stream is then passed via a conduit 352to a CO₂ electrolysis module 330 for conversion of at least a portion ofthe gas stream. In particular embodiments, the post-CO-consuming processgaseous substrate is passed via a conduit 342 to the one or more removalmodule 320 that receives the CO₂-comprising gas from the industrialprocess 310. In various embodiments, the post-CO-consuming processgaseous substrate may be passed to the one or more removal module 320that receives the CO₂-comprising gas from the industrial process 310 andthe one or more removal module 350.

The CO-consuming process 340 of FIG. 3 may be a gas fermentation processand may occur in an inoculator and/or one or more bioreactors. Forexample, the CO-consuming process may be a gas fermentation process in abioreactor comprising a culture of at least one C1-fixing microorganism.In the CO-consuming process 340, the culture is fermented to produce oneor more fermentation products 346 and a post-CO-consuming processgaseous substrate.

In particular embodiments, a CO₂ concentration module may be placedafter a removal module. FIG. 4 shows a process for integration of anindustrial process 410 with a removal module 420, an optional CO₂concentration module 470, a CO₂ electrolysis module 430, an optional H₂electrolysis module 480, a CO-consuming process 440, and an optional O₂separation module 460, in accordance with one aspect of the invention.In embodiments not including an optional CO₂ concentration module 470,CO₂-comprising gas from the industrial process 410 is fed from theremoval module 420 to the CO₂ electrolysis module 430 via a conduit 422.In embodiments including an optional CO₂ concentration module 470,CO₂-comprising gas from the industrial process 410 is fed via a conduit412 to one or more removal module 420 to remove and/or convert one ormore constituent 428. The treated stream is then fed via a conduit 424to an optional CO₂ concentration module 470 in order to increase theconcentration of the CO₂ in the gas stream and remove one or moreconstituent 474. The CO₂-concentrated gas stream is then fed via aconduit 472 to a CO₂ electrolysis module 430 for conversion of at leasta portion of the gas stream. At least a portion of the converted gasstream may be passed from the CO₂ electrolysis module 430 to theCO-consuming process 440 via a conduit 432. In some embodiments, theconstituent 474 is CO and/or H₂, which is passed via conduit 476 to theCO-consuming process 440. In some embodiments, a water substrate is fedvia a conduit 482 to an H₂ electrolysis module 480 for conversion of atleast a portion of the water substrate, and an H₂-enriched stream ispassed via a conduit 484 to the CO-consuming process 440. Optionally, atleast a portion of O₂ may be fed from the H₂ electrolysis module 480 tothe industrial process 410 via a conduit 486.

At least a portion of the gas stream from the CO₂ electrolysis module430 may be passed to the industrial process 410 via conduit 436. Inparticular embodiments, the process includes an O₂ separation module 460following the CO₂ electrolysis module 430 to separate at least a portionof O₂ from the gas stream. In embodiments including an O₂ separationmodule 460 following the CO₂ electrolysis module 430, the gas stream isfed via a conduit 434 from the CO₂ electrolysis module 430 to the O₂separation module 460. In embodiments utilizing an O₂ separation module460 after the CO₂ electrolysis module 430, at least a portion of the gasstream is fed from the O₂ separation module 460 to the industrialprocess 410 via a conduit 464. In embodiments utilizing an O₂ separationmodule 460 after the CO₂ electrolysis module 430, at least a portion ofthe O₂-lean stream is fed from the O₂ separation module 460 to theCO-consuming process via a conduit 462. In some embodiments utilizing anO₂ separation module 460 after the CO₂ electrolysis module 430, at leasta portion of the O₂-lean stream is fed from the O₂ separation module 460back to the CO₂ electrolysis module 430 via a conduit 466. Inembodiments not utilizing an O₂ separation module 460, a portion of thegas stream may be fed from the CO₂ electrolysis module 430 to theindustrial process 410 via a conduit 436.

In some embodiments, the CO-consuming process 440 of FIG. 4 comprises aCO₂-producing reaction step. In embodiments wherein a post-CO-consumingprocess gaseous substrate comprises CO₂, at least a portion of thepost-CO-consuming process gaseous substrate is passed via a conduit 442to one or more removal module 450 to remove and/or convert one or moreconstituent 458. The treated gas stream is then passed via a conduit 452to a CO₂ electrolysis module 430 for conversion of at least a portion ofthe gas stream. In particular embodiments, the post-CO-consuming processgaseous substrate is passed via a conduit 442 to the same one or moreremoval module 420 that receives the CO₂-comprising gas from theindustrial process 410. In various embodiments, the post-CO-consumingprocess gaseous substrate may be passed to the one or more removalmodule 420 that receives the CO₂-comprising gas from the industrialprocess 410 and the one or more removal module 450.

The CO-consuming process 440 of FIG. 4 may be a gas fermentation processand may occur in an inoculator and/or one or more bioreactors. Forexample, the CO-consuming process 440 may be a gas fermentation processin a bioreactor comprising a culture of at least one C1-fixingmicroorganism. In embodiments wherein the CO-consuming process 440 is agas fermentation process, a culture may be fermented to produce one ormore fermentation products 446 and a post-fermentation gaseous substrate(CO-consuming process gaseous substrate).

FIG. 5 shows a process for integration of an industrial process 510 witha removal module 520, optional CO₂ concentration modules 570, a CO₂electrolysis module 530, a CO-consuming process 540, an optional O₂separation module 560, an optional pressure module 580, and an optionalH₂ electrolysis module 1500, in accordance with one aspect of theinvention. CO₂-comprising gas from the industrial process 510 is fed viaa conduit 512 to one or more removal module 520 to remove and/or convertone or more constituent 528. The treated gas from the one or moreremoval module 520 is then fed via a conduit 522 to a CO₂ electrolysismodule 530 for conversion of at least a portion of the gas stream. Inembodiments that blend H₂, a hydrolysis electrolysis module 1500 maysend an H₂-rich gas stream, via a conduit 1502, to be blended with theconverted gas stream prior to the converted gas stream prior to thebeing introduced to the CO-consuming process 540.

In particular embodiments, the invention provides one or more pressuremodule 580 to increase the pressure of the converted gas from the CO₂electrolysis module 530. In embodiments utilizing a pressure module 580after the CO₂ electrolysis module 530, at least a portion of the gasstream is fed from the CO₂ electrolysis module 530 to the pressuremodule 580 via a conduit 532. The pressure module 580 increases thepressure of the gas stream and passes the gas stream to the CO-consumingprocess 540, via a conduit 582.

In various embodiments, the H₂ electrolysis module 1500 is incorporatedwith an O₂ separation module 560 and/or a pressure module 580. Invarious embodiments, a water substrate is fed via a conduit 1506 to theH₂ electrolysis module 1500, and the H₂ electrolysis module may send anH₂-rich gas stream, via a conduit 1502, to be blended with the convertedgas stream prior to the gas stream being introduced to the CO-consumingprocess 540. In particular embodiments, the conduit 1502 for sending theH₂-rich gas stream is connected with the conduit 582 for sending thepressurized CO-rich stream to provide for blending of the streams. Invarious embodiments, the H₂ electrolysis module 1500 sends an H₂-richgas stream directly to the CO-consuming process 540 via a conduit 1504.Optionally, at least a portion of O₂ may be fed from the H₂ electrolysismodule 1500 to the industrial process 510 via a conduit 1508.

In certain embodiments, the invention integrates an industrial process510, an optional CO₂ concentration module 570, a removal module 520, aCO₂ electrolysis module 530, an optional O₂ separation module 560, anoptional pressure module 580, an H₂ electrolysis module 1500, and aCO-consuming process 540, in accordance with one aspect of theinvention. CO₂-comprising gas from the industrial process 510 is fed viathe conduit 514 to an optional CO₂ concentration module 570 to increasethe concentration of the CO₂ in the gas stream and remove one or moreconstituent 574. The optional CO₂ concentration module 570 sends the gasto the removal module 520, via a conduit 572, to remove and/or convertone or more constituent 528. The treated stream is then fed via aconduit 524 to an optional CO₂ concentration module 570 to increase theconcentration of the CO₂ in the gas stream and remove one or moreconstituent 574. The optional CO₂ concentration module 570 sends thegas, via a conduit 572, to a CO₂ electrolysis module 530 for conversionof at least a portion of the gas stream. At least a portion of theconverted gas stream may be passed to an optional O₂ separation module560, via a conduit 534, to separate at least a portion of O₂ from thegas stream. At least a portion of the O₂-rich gas stream may be passedfrom the optional O₂ separation module 560 to the industrial process510, via a conduit 564. At least a portion of the O₂-rich gas stream maybe fed from the CO₂ electrolysis module 530 to the industrial process510 via a conduit 536. At least a portion of the O₂-depleted gas streammay be passed from the optional O₂ separation module 560 to an optionalpressure module 580, via a conduit 562. The gas stream from the optionalpressure module 580 is sent, via a conduit 582, to the CO-consumingprocess 540. The gas stream may be blended with an H₂-rich gas streamprior to being introduced to the CO-consuming process 540. Preferably,the H₂-rich gas stream is passed from an H₂ electrolysis module 1500 viaa conduit 1502.

The CO-consuming process 540 of FIG. 5 produces a product 546. TheCO-consuming process may be a gas fermentation process and may occur inan inoculator and/or one or more bioreactors. For example, theCO-consuming process may involve fermenting a culture to produce one ormore fermentation product 546 and a post-fermentation gaseous substrate(post-CO-consuming process gaseous substrate). The post-CO-consumingprocess gaseous substrate may be passed via a conduit 542 to the removalmodule 550 to remove and/or convert one or more constituent 558. Inembodiments including a CO₂ concentration module 570 after theCO-consuming process, the post-CO-consuming process gaseous substratemay be passed via a conduit 544 to an optional CO₂ concentration module570 to increase the concentration of the CO₂ in the gas stream andremove one or more constituent 574. The optional CO₂ concentrationmodule 570 may send the post-CO-consuming process gaseous substrate tothe removal module 550, via a conduit 572, to remove and/or convert oneor more constituent 558. The treated gas stream may then be passed via aconduit 552 to a CO₂ electrolysis module 530 for conversion of at leasta portion of the gas stream. In particular embodiments, thepost-CO-consuming process gaseous substrate is passed, via a conduit 542to the same one or more removal module 520 that receives theCO₂-comprising gas from the industrial process 510. In variousembodiments, the post-CO-consuming process gaseous substrate may bepassed to both the one or more removal module 520 that receives theCO₂-comprising gas from the industrial process 510 and the one or moreremoval module 550.

The invention provides generally for the removal of constituents fromthe gas stream that may have adverse effects on downstream processes,for instance, the downstream fermentation process and/or downstreammodules. In particular embodiments, the invention provides for one ormore further removal module between the various modules in order toprevent the occurrence of such adverse effects.

In various instances, the conversion of a CO₂-comprising gaseoussubstrate by an CO₂ electrolysis module results in one or moreconstituent passing through the CO₂ electrolysis module 630. In variousembodiments, this results in one or more constituent in the CO-enrichedstream. In certain instances, the constituent includes portions ofconverted O₂. In various embodiments, the further removal module is adeoxygenation module for removing O₂ from the CO-enriched stream.

FIG. 6 shows the integration of a CO₂ electrolysis module 630, anoptional O₂ separation module 660, an optional pressure module 680, witha further removal module 690. In certain instances, the further removalmodule 690 is utilized following the CO₂ electrolysis module 630. Inembodiments utilizing a further removal module 690 after the CO₂electrolysis module 630, at least a portion of the gas stream is fedfrom the CO₂ electrolysis module 630 to the further removal module 690via a conduit 632. The further removal module 690 removes and/orconverts one or more constituent 698 in the gas stream. Additionally,when utilizing an optional O₂ separation module 660, the O₂ separationmodule 660 sends the gas stream via a conduit 662 to the further removalmodule 690 to remove and/or convert one or more constituent 698. Thetreated stream is then fed, via a conduit 692, to an optional pressuremodule 680.

In certain embodiments, the invention integrates an industrial process610, an optional CO₂ concentration module 670, a removal module 620, aCO₂ electrolysis module 630, a further removal module 690, an optionalO₂ separation module 660, an optional pressure module 680, an optionalH₂ electrolysis module 1600, and a CO-consuming process 640, inaccordance with one aspect of the invention. In embodiments notincluding an optional CO₂ concentration module 670 between theindustrial process 610 and the removal module 620, the CO₂-comprisinggas from the industrial process 610 is fed via a conduit 612 to theremoval module 620. In embodiments including an optional CO₂concentration module 670 between the industrial process 610 and theremoval module 620, the CO₂-comprising gas from the industrial process610 is fed via the conduit 614 to an optional CO₂ concentration module670 to increase the concentration of the CO₂ in the gas stream andremove one or more constituent 674. The optional CO₂ concentrationmodule 670 sends the gas to the removal module 620, via a conduit 672,to remove and/or convert one or more constituent 628. In embodiments notincluding a CO₂ concentration module 670 between the removal module 620and the CO₂ electrolysis module 630, the treated stream is fed via aconduit 622 from the removal module 620 to the CO₂ electrolysis module630. In embodiments including a CO₂ concentration module 670 between theremoval module 620 and the CO₂ electrolysis module 630, the treatedstream is then fed via a conduit 624 to an optional CO₂ concentrationmodule 670 to increase the concentration of the CO₂ in the gas streamand remove one or more constituent 674. The optional CO₂ concentrationmodule 670 sends the gas, via a conduit 672, to a CO₂ electrolysismodule 630 for conversion of at least a portion of the gas stream. Atleast a portion of the O₂-rich gas stream may be fed from the CO₂electrolysis module 630 to the industrial process 610 via a conduit 636.At least a portion of the CO-rich gas stream may be passed via a conduit632 to a further removal module 690 to remove and/or convert one or moreconstituent 698. At least a portion of the treated gas stream may bepassed via a conduit 634 to an optional O₂ separation module 660 toseparate at least a portion of O₂ from the gas stream. At least aportion of the O₂-rich gas stream may be passed via a conduit 664 fromthe optional O₂ separation module 660 to the industrial process 610. Atleast a portion of the gas stream may be passed from the optional O₂separation module 660 via a conduit 662 to the further removal module690 to remove and/or convert one or more constituent 698. At least aportion of the gas stream may be passed from the further removal module690, via a conduit 692, to an optional pressure module 680. The gasstream from the optional pressure module 680 is sent, via a conduit 682,to the CO-consuming process 640. The gas stream may be blended with anH₂-rich gas stream prior to being introduced to the CO-consuming process640. Preferably, a water substrate is passed via a conduit 1606 to an H₂electrolysis module 1600, and an H₂-rich gas stream is passed from an H₂electrolysis module 1600 via a conduit 1602. In various embodiments, theH₂ electrolysis module 1600 sends an H₂-rich gas stream directly to theCO-consuming process 640 via a conduit 1604. In some embodiments, O₂produced by the H₂ electrolysis module 1600 is passed via conduit 1608to the industrial process 610.

The CO-consuming process 640 of FIG. 6 may produce a product 646. TheCO-consuming process may be a gas fermentation process and may occur inan inoculator and/or one or more bioreactors. For example, theCO-consuming process may involve fermenting a culture to produce one ormore fermentation product 646 and a post-fermentation gaseous substrate(post-CO-consuming process gaseous substrate. The post-CO-consumingprocess gaseous substrate is passed via a conduit 644 to an optional CO₂concentration module 670 to increase the concentration of the CO₂ in thegas stream and remove one or more constituent 674. The optional CO₂concentration module 670 sends the post-CO-consuming process gaseoussubstrate to the removal module 650, via a conduit 672, to remove and/orconvert one or more constituent 658. The treated gas stream is thenpassed via a conduit 652 to a CO₂ electrolysis module 630 for conversionof at least a portion of the gas stream. In particular embodiments, thepost-CO-consuming process gaseous substrate is passed, via a conduit 642to the same one or more removal module 620 that receives theCO₂-comprising gas from the industrial process 610. In variousembodiments, the post-CO-consuming process gaseous substrate may bepassed to the one or more removal module 620 that receives theCO₂-comprising gas from the industrial process 610 and the one or moreremoval module 650.

In various embodiments, the invention provides an integrated processcomprising electrolysis wherein the power supplied for the electrolysisprocess is derived, at least in part, from a renewable energy source.

Although the substrate is typically gaseous, the substrate may also beprovided in alternative forms. For example, the substrate may bedissolved in a liquid saturated with a CO-comprising gas using amicrobubble dispersion generator. By way of further example, thesubstrate may be adsorbed onto a solid support.

The C1-fixing microorganism in a bioreactor is typically acarboxydotrophic bacterium. In particular embodiments, thecarboxydotrophic bacterium is selected from the group comprisingMoorella, Clostridium, Ruminococcus, Acetobacterium, Eubacterium,Butyribacterium, Oxobacter, Methanosarcina, Methanosarcina, andDesulfotomaculum. In various embodiments, the carboxydotrophic bacteriumis Clostridium autoethanogenum.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein. The reference to any prior art in this specification is not, andshould not be taken as, an acknowledgement that that prior art formspart of the common general knowledge in the field of endeavour in anycountry.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to”) unless otherwise noted. The term “consistingessentially of” limits the scope of a composition, process, or method tothe specified materials or steps, or to those that do not materiallyaffect the basic and novel characteristics of the composition, process,or method. The use of the alternative (i.e., “or”) should be understoodto mean either one, both, or any combination thereof of thealternatives. As used herein, the term “about” means±20% of theindicated range, value, or structure, unless otherwise indicated.

Recitation of ranges of values herein are merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range, unless otherwise indicated herein, and eachseparate value is incorporated into the specification as if it wereindividually recited herein. For example, any concentration range,percentage range, ratio range, integer range, size range, or thicknessrange is to be understood to include the value of any integer within therecited range and, when appropriate, fractions thereof (such as onetenth and one hundredth of an integer), unless otherwise indicated.

All methods described herein can be performed in any suitable orderunless otherwise indicated herein or otherwise clearly contradicted bycontext. The use of any and all examples, or exemplary language (i.e.,“such as”) provided herein, is intended merely to better illuminate theinvention and does not pose a limitation on the scope of the inventionunless otherwise claimed. No language in the specification should beconstrued as indicating any non-claimed element as essential to thepractice of the invention.

Preferred embodiments of this invention are described herein. Variationsof those preferred embodiments may become apparent to those of ordinaryskill in the art upon reading the foregoing description. The inventorsexpect skilled artisans to employ such variations as appropriate, andthe inventors intend for the invention to be practiced otherwise than asspecifically described herein. Accordingly, this invention includes allmodifications and equivalents of the subject matter recited in theclaims appended hereto as permitted by applicable law. Moreover, anycombination of the above-described elements in all possible variationsthereof is encompassed by the invention unless otherwise indicatedherein or otherwise clearly contradicted by context.

1. A process for improving carbon conversion efficiency, wherein theprocess comprises: a. passing a CO₂-comprising gaseous substrate from anindustrial process to a first removal module for removal of at least oneconstituent from the CO₂-comprising gaseous substrate to produce a firstCO₂-treated gas stream; b. passing the first CO₂-treated gas stream to aCO₂ electrolysis module for conversion of at least a portion of thefirst CO₂-treated gas stream to produce a CO-enriched stream and a firstO₂-enriched stream; and c. passing at least a portion of the CO-enrichedstream to a CO-consuming process.
 2. The process of claim 1, wherein theCO₂-comprising gaseous substrate from the industrial process is firstpassed to a pressure module to produce a pressurized CO₂-comprising gasstream, and the pressurized CO₂-comprising gas stream is passed to thefirst removal module.
 3. The process of claim 1, wherein the processfurther comprises one or more of: a. passing at least a portion of thefirst O₂-enriched stream directly to the industrial process; and b.passing at least a portion of the first O₂-enriched stream to an O₂separation module to produce a second O₂-enriched stream and an O₂-leanstream.
 4. The process of claim 3, wherein the process further comprisesone or more of: a. passing at least of portion of the second O₂-enrichedstream to the industrial process; b. passing at least of portion of theO₂-lean stream to the CO₂ electrolysis module; and c. passing at leastof portion of the O₂-lean stream to the CO-consuming process.
 5. Theprocess of claim 1, wherein the process further comprises passing atleast a portion of the CO₂-comprising gaseous substrate from theindustrial process and/or at least a portion of the first CO₂-treatedgas stream to a first CO₂ concentration module to produce a firstCO₂-concentrated stream and a first CO₂-lean stream.
 6. The process ofclaim 5, wherein the process further comprises passing at least aportion of the first CO₂-concentrated stream to one or more of the firstremoval module and the CO₂ electrolysis module.
 7. The process of claim5, wherein the first CO₂-lean stream comprises CO and/or H₂ and whereinthe process further comprises passing at least a portion of the firstCO₂-lean stream to the CO-consuming process.
 8. The process of claim 1,wherein the process comprises passing at least a portion of theCO-enriched stream to a pressure module to produce a pressurizedCO-stream and passing at least a portion of the pressurized CO-stream tothe CO-consuming process.
 9. The process of claim 1, wherein the processfurther comprises passing a water substrate to an H₂ electrolysis moduleto produce an H₂-enriched stream and passing at least a portion of theH₂-enriched stream to the CO-consuming process.
 10. The process of claim1, wherein the CO-consuming process produces a tail gas comprising CO₂.11. The process of claim 10, wherein the process further comprises oneor more of: a. passing at least a portion of the tail gas comprising CO₂to the first removal module or to a second removal module for removal ofat least one constituent from the tail gas to produce a secondCO₂-treated gas stream; and b. passing at least a portion of the tailgas comprising CO₂ to a second CO₂ concentration module to produce asecond CO₂-concentrated stream and a second CO₂-lean stream.
 12. Theprocess of claim 11, wherein at least a portion of the tail gascomprising CO₂ is passed to a pressure module to produce a pressurizedtail gas stream, and the pressurized tail gas stream is passed to thefirst removal module and/or the second removal module.
 13. The processof claim 11, wherein the process further comprises passing at least aportion of the second CO₂-concentrated stream to the first removalmodule or to the second removal module for removal of at least oneconstituent from the tail gas to produce a second CO₂-treated gasstream.
 14. The process of claim 13, wherein the process furthercomprises passing at least a portion of the second CO₂-treated gasstream to the CO₂ electrolysis module.
 15. The process of claim 1,wherein the CO₂-comprising gaseous substrate from the industrial processfurther comprises one or more of CO, H₂, and CH₄.
 16. The process ofclaim 1, wherein the industrial process is selected from the groupcomprising carbohydrate fermentation, gas fermentation, cement making,pulp and paper making, steel making, oil refining and associatedprocesses, petrochemical production, coke production, anaerobic oraerobic digestion, gasification, natural gas extraction, oil extraction,metallurgical processes, production and/or refinement of aluminum,copper, and/or ferroalloys, geological reservoirs, Fischer-Tropschprocesses, methanol production, pyrolysis, steam methane reforming, drymethane reforming, partial oxidation of biogas or natural gas, andautothermal reforming of biogas or natural gas.
 17. The process of claim1, wherein the first removal module is selected from the groupconsisting of a hydrolysis module, an acid gas removal module, adeoxygenation module, a catalytic hydrogenation module, a particulateremoval module, a chloride removal module, a tar removal module, and ahydrogen cyanide polishing module.
 18. The process of claim 1, whereinthe at least one constituent removed from the CO₂-comprising gassubstrate is selected from the group consisting of sulfur compounds,aromatic compounds, alkynes, alkenes, alkanes, olefins, nitrogencompounds, oxygen, phosphorous-comprising compounds, particulate matter,solids, oxygen, halogenated compounds, silicon-comprising compounds,carbonyls, metals, alcohols, esters, ketones, peroxides, aldehydes,ethers, tars, and naphthalene.
 19. The process of claim 1, wherein theCO-consuming process is a fermentation process comprising a culture ofat least one carboxydotrophic bacterium.
 20. The process of claim 19,wherein the fermentation process produces a fermentation productselected from the group consisting of ethanol, butyrate, 2,3-butanediol,lactate, butene, butadiene, methyl ethyl ketone, ethylene, acetone,isopropanol, lipids, 3-hydroypropionate, terpenes, fatty acids,2-butanol, 1,2-propanediol, and 1-propanol.